JP2016155719A - Method for manufacturing porous gypsum hardened body and water purifying material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method making it possible to easily and inexpensively manufacture a porous gypsum hardened body having low density and a large surface area, and having a porous structure made up of open pores.SOLUTION: A method for manufacturing a porous gypsum hardened body uses at least gypsum, a water-soluble material, and water. The method for manufacturing the porous gypsum hardened body includes at least: preparing a slurry containing gypsum, a water-soluble material, and water; obtaining a molded product from the slurry; and washing with water.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a cured porous gypsum and a water purification material.

With the expectation of application to building materials (so-called gypsum board) and water purification materials, etc., studies have been made on the porous structure and low density of hardened gypsum. For example, Patent Document 1 discloses a method for producing a low-density gypsum hardened body using a dispersing agent such as fine fibrous cellulose or bentonite, and Patent Document 2 uses sodium hydrogen carbonate as a foaming agent. A method for producing a gypsum porous structure is disclosed. Patent Document 3 discloses a method for foaming by adding gypsum to water containing a foaming agent obtained by blending an ethylene oxide adduct of alcohol with an anionic surfactant for the production of lightweight gypsum board.

JP 2012-116147 A JP 2013-189347 A JP-A-7-291176

However, low-density gypsum hardened bodies and porous structures manufactured by conventional techniques are not suitable for water purification materials because they have a closed pore structure to be described later. There is also concern about an increase in manufacturing costs. For example, according to Patent Documents 1 and 2, since it is necessary to blend a material such as a dispersant and a foaming agent into gypsum, the manufacturing cost tends to increase. Similarly, the organic foaming agent of Patent Document 3 has a problem in terms of cost, and also requires an operation for foaming. Therefore, a technique for solving these problems has been demanded.

The present invention provides a method capable of easily and inexpensively producing a cured porous gypsum body having a low density, a high surface area, and a porous structure composed of open pores, in view of the above-described present situation. For the purpose.

While the inventors have made various studies on the porous structure and density reduction of a hardened gypsum body, a slurry containing gypsum, a water-soluble substance and water is prepared, molded, and then washed with water. Thus, it has been found that a porous gypsum cured body having a low density and a high surface area can be produced very simply and inexpensively, and the obtained porous gypsum cured body has a porous structure composed of open pores. As a result, the present invention has been completed.

Here, when a gypsum porous structure is produced using a foaming agent as in Patent Document 2, closed pores (pores that are independent inside the object) are generated in which bubbles are included in the gypsum and solidified. It is considered that a porous structure is constituted by closed pores. On the other hand, in the production method of the present invention, a water-soluble substance is eluted by performing a washing step with water, thereby forming a porous structure. Therefore, the porous structure is formed by open pores (pores connected to the outside). The structure is structured. Therefore, the hardened porous gypsum obtained by the production method of the present invention can secure a high surface area while having an extremely low density, and thus works more advantageously as, for example, an adsorbent or a recovery material for a specific element in waste water. It is considered a thing.

That is, the present invention is a method for producing a cured porous gypsum using at least gypsum, a water-soluble substance and water,
The manufacturing method is as follows:
A slurry preparation step of preparing a slurry containing gypsum, a water-soluble substance and water;
A molding step of obtaining a molding from the slurry;
A method for producing a cured porous gypsum body comprising at least a washing step of washing with water.

The water-soluble substance is preferably a non-foaming inorganic substance, and more preferably a metal salt. Since such water-soluble substances are easily available and generally cheaper than organic substances, it is possible to produce a porous gypsum hardened body having a porous structure with open pores more easily and inexpensively. The resulting porous gypsum hardened body has a much lower density and a higher surface area.

The water-soluble substance is preferably at least one selected from the group consisting of sodium chloride and potassium chloride. This makes it possible to produce a hardened porous gypsum having a porous structure with open pores having a low density and a high surface area, more easily and inexpensively.

The slurry preferably contains the water-soluble substance in an amount equal to or higher than the saturation solubility at the temperature at which the slurry is produced. Thereby, the porous gypsum hardened body in which the porous structure is configured with open pores having a lower density and a higher surface area can be easily obtained.

The slurry preferably contains 40 to 2000 parts by weight of water with respect to 100 parts by weight of gypsum. Thereby, the porous gypsum hardened body in which the porous structure is configured with open pores having a lower density and a higher surface area can be easily obtained.

The porous gypsum hardened body preferably has an open porosity of 50% or more. Such a porous gypsum hardened body becomes more useful, for example, for various uses described later.

The present invention is also a water purification material using the cured porous gypsum obtained by the above production method. Such a water purification material is extremely excellent in adsorption performance / support performance of various elements (for example, P, Pb, As, etc.), and thus is useful for purification treatment of water such as drainage, sewage, and rivers.

By the method for producing a cured porous gypsum according to the present invention, a cured porous gypsum having a low density, a high surface area, and a porous structure constituted by open pores can be produced very simply and inexpensively. . Therefore, the porous gypsum hardened body obtained by the production method of the present invention is useful for various uses such as building materials and water purification materials. In particular, it has excellent adsorption performance and loading performance for various elements (eg, P, Pb, As, etc.) due to its low density and high surface area. It is extremely useful for applications.

FIG. 1 is a photograph taken in an oblique direction on the front, with the hardened gypsum bodies obtained in Examples 1 to 4 and Comparative Example 1 each having a cylindrical shape (about 1 g, diameter about 1.5 cm). FIG. 2 is a photograph (front photograph) taken from the front direction with the hardened gypsum bodies obtained in Examples 1 to 4 and Comparative Example 1 each having a cylindrical shape (about 1 g, diameter about 1.5 cm). FIG. 3 is a photograph (planar photograph) taken from above with the gypsum cured bodies obtained in Examples 1 to 4 and Comparative Example 1 each having a cylindrical shape (about 1 g, diameter of about 1.5 cm).

Hereinafter, an example of the present invention will be described in detail. However, the present invention is not limited to the following description, and can be applied as appropriate without departing from the scope of the present invention.

The method for producing a cured porous gypsum according to the present invention includes (1) a slurry preparation step for preparing a slurry containing gypsum, a water-soluble substance and water, (2) a molding step for obtaining a molded product from the slurry, and (3 ) A washing step of washing with water, but may contain one or more other steps as necessary. Other steps are not particularly limited.

(1) Slurry preparation process First, a slurry preparation process is demonstrated.
The slurry preparation step is a step of preparing a slurry (also referred to as a suspension) containing gypsum, a water-soluble substance, and water. The production method is not particularly limited, and it is preferable to stir so that the raw materials are uniformly mixed. Moreover, although the temperature at the time of slurry preparation is not specifically limited, For example, it is preferable to produce a slurry at 5-35 degreeC from a work surface.

The slurry contains gypsum, a water-soluble substance, and water, but may contain other components as long as the effects of the present invention are not impaired.
In addition, each content component can use 1 type (s) or 2 or more types, respectively.

It is not particularly restricted but includes gypsum, which comprises at least a hemihydrate gypsum _{(CaSO 4 · 1 / 2H 2} O) is preferred. Hemihydrate gypsum reacts with water to hydrate and solidify into dihydrate gypsum (CaSO ₄ .2H ₂ O). Moreover, hemihydrate gypsum is the main component and anhydrous gypsum (CaSO ₄ ) and various inorganic substances (for example, metal compounds such as calcium carbonate, zinc oxide, and titanium hydroxide) may be included. In particular, it is expected that by further including (or supporting) an inorganic substance, it is possible to improve the adsorption performance of phosphorus and to efficiently adsorb substances that cannot be adsorbed only with gypsum such as sulfides and radioactive substances. In particular, when gypsum containing hemihydrate gypsum and calcium carbonate is used, the resulting porous gypsum hardened body is extremely useful as an adsorbent or recovery material for a specific element such as phosphorus.

The method for containing or supporting the inorganic material in the gypsum is not particularly limited, and the inorganic material may be blended in the slurry preparation step. After the porous gypsum cured body is created, the cured body may be used as a slurry or an aqueous solution containing the inorganic substance. May be impregnated.

The water-soluble substance is a water-soluble substance. Water-soluble means a property of dissolving 1 g or more with respect to 100 g of water at a temperature of 25 ° C., and preferably the amount of dissolution is 10 g or more, more preferably 20 g or more.

The water-soluble substance is preferably a non-foaming inorganic substance. Non-foaming means that no gas (gas) such as carbon dioxide is generated from the water-soluble substance itself or by decomposition by a reaction such as heating or neutralization. By using a non-foaming inorganic substance, the resulting porous gypsum hardened body has a higher open porosity. Among these, a metal salt is preferable. Since such water-soluble substances are easily available and expensive foaming agents and foaming agents are unnecessary, it is possible to produce a hardened porous gypsum body more easily and inexpensively, and to obtain a porous gypsum cured product. The body will have a much higher open porosity.

Examples of the metal salt include hydroxides such as KOH, NaOH, Ba (OH) ₂ and LiOH; ZnCl ₂ , AlCl ₃ , CaCl ₂ , SrCl ₂ , FeCl ₂ , FeCl ₃ , CuCl ₂ , BaCl ₂ , MgCl ₂ , chlorides such as MnCl ₂ , MnCl ₃ , MnCl ₄ , NaCl, KCl; ZnSO ₄ , Al ₂ (SO ₄ ) ₃ , K ₂ SO ₄ , Zr (SO ₄ ) ₂ , CuSO ₄ , Na ₂ SO ₄ , Sulfates such as MgSO ₄ and MnSO ₄ ; Zn (NO ₃ ) ₂ , Al (NO ₃ ) ₃ , KNO ₃ , Ca (NO ₃ ) ₂ , Sr (NO ₃ ) ₂ , Cu (NO ₃ ) ₂ , NaNO ₃ , Ba (NO ₃ ) ₂ , Mg (NO ₃ ) ₂ , Mn (NO ₃ ) _{2 and} other nitrates; Zn (C ₂ H ₃ O ₂ ) ₂ , KC ₂ H ₃ O ₂ , Ca ( Acetic acid salts such as C ₂ H ₃ O ₂ ) ₂ , Sr (C ₂ H ₃ O ₂ ) ₂ , NaCH ₃ CO ₂ , Ba (C ₂ H ₃ O ₂ ) ₂ , Mg (C ₂ H ₃ O ₂ ) ₂ And the like. Among these, chloride is preferable from the viewpoint of making the porous structure easier.

The water-soluble substance is particularly preferably at least one selected from the group consisting of sodium chloride (NaCl) and potassium chloride (KCl). By using such a water-soluble substance, it is possible to produce a porous gypsum hardened body more easily and inexpensively, and the obtained porous gypsum hardened body has a much lower density and a high surface area. Become.

The size (median particle size) of the water-soluble substance is not particularly limited, but this size can affect the open pore size in the obtained porous gypsum cured product, so that the desired open pore size is obtained. It is preferable to select the size of the water-soluble substance (median particle size). For example, the porous gypsum hardened body more suitable for water purification material use preferably has an open pore diameter (median value) of 0.01 to 2 mm. However, a porous gypsum hardened body having such an open pore diameter is preferably used. In order to obtain it, it is preferable that the median particle diameter of a water-soluble substance is 0.01-2 mm. More preferably, the median particle size of the water-soluble substance is 0.1 to 1 mm.

In the present specification, the median particle size of the water-soluble substance can be determined according to a dry screening test in JIS Z8815 (1994) [General rules of screening test method]. The open pore diameter (median value) of the cured porous gypsum can be measured by performing imaging and image processing from directly above with a stereomicroscope camera.

In the slurry, the content of the water-soluble substance is preferably equal to or higher than the saturation solubility at the temperature at the time of slurry preparation. Thereby, the porous gypsum hardened body made more porous and reduced in density can be easily obtained. More preferably, the amount is 1.5 times or more the saturation solubility at the temperature at the time of slurry preparation, and more preferably an amount that is 2 times or more the saturation solubility. Further, the upper limit of the content of the water-soluble substance is not particularly limited, but for example, from the viewpoint of facilitating the subsequent washing step, the amount is preferably 10 times or less of the saturation solubility at the temperature during slurry preparation. . Needless to say, the saturated solubility is a saturated solubility of a water-soluble substance at a temperature at the time of slurry preparation with respect to water contained in the slurry.
More specifically, for example, sodium chloride (solubility in water: 35.9 g / 100 g (25 ° C.)) is used as the water-soluble substance, and the slurry is 25 ° C. “Amount equal to or higher than the saturation solubility at the temperature at the time of production” means 35.9 parts by weight or more with respect to 100 parts by weight of water.

Moreover, in the said slurry, it is preferable that content of water shall be 40-2000 weight part with respect to 100 weight part of gypsum. Thereby, the porous gypsum hardened body made more porous and reduced in density can be easily obtained. More preferably, it is 50-1000 weight part, More preferably, it is 60-500 weight part. Moreover, you may adjust the viscosity of a slurry according to the shaping | molding method in a shaping | molding process.

The other components are not particularly limited. For example, pulp fibers such as linter pulp, softwood pulp, and hardwood pulp; dispersion aids such as surfactants such as puffade (formalin condensate of amino acids, manufactured by Ajinomoto Co.); Organic fiber (acrylic fiber, vinylon fiber, etc.); inorganic fiber (rock wool, glass fiber, carbon fiber, etc.); enzyme (proteolytic enzyme, lipolytic enzyme, starch degrading enzyme, fiber degrading enzyme, etc.); starch (corn starch, Potato starch, wheat starch, rice starch, tapioca starch, sago starch, modified starch, etc.); binders such as PVA (polyvinyl alcohol), methylcellulose; inorganic lightweight aggregates such as perlite, shirasu balloon, vermiculite, glass balloon; colorant ; Setting retarder such as sodium citrate, citric acid, gelatin, glue, etc .; Hardening accelerator Rebaking inhibitor; adhesive; leveling agent; non-leveling agent; thickener; bactericidal agent; fungicidal agent; pH adjuster; coloring agent; reinforcing material; flame retardant; Etc.
Although content of another component is not specifically limited, For example, it is preferable to set it as 10 weight part or less in 100 weight part of slurries.

(2) Molding process The molding process (also referred to as a molding process) is a process for obtaining a molded product by molding the slurry obtained in the slurry production process. The molding method and conditions are not particularly limited, and examples thereof include a method of pouring the slurry into a mold, a method of applying a viscous slurry to one or more layers on a belt conveyor, or a method of granulating. What is necessary is just to set suitably so that sum reaction may fully advance and a slurry may harden | cure. For example, after pouring the slurry into a mold, it is preferably left at 10 to 100 ° C. for 0.5 to 50 hours.

The molding temperature (also referred to as the curing temperature) can affect the open pore size (median value) in the cured porous gypsum body, so set the cure temperature to the desired open pore size. Is preferred. For example, the porous gypsum hardened body more suitable for water purification material use preferably has an open pore diameter (median value) of 0.01 to 2 mm. However, a porous gypsum hardened body having such an open pore diameter is preferably used. In order to obtain it, it is preferable that a curing temperature shall be 10-100 degreeC. The curing temperature is more preferably 20 to 80 ° C.

In this invention, it is suitable to perform a drying process after performing a shaping | molding process. The drying method and conditions are not particularly limited, and it is preferable to carry out the drying until the weight of the gypsum hardened body does not change under the drying conditions (that is, until the weight becomes constant). It is also preferable to set the drying conditions so that the materials are sufficiently dried even when the mixing ratio of the raw materials is different. For example, it is preferable to dry for 0.5 to 50 hours with a dryer at 30 to 80 ° C.

(3) Washing process The washing process is a process of washing a molded product obtained by the molding process (including those obtained through a drying process and other processes after the molding process) with water. By washing with water, water-soluble substances precipitated in the molding process and drying process are eluted, thereby forming a porous structure. There is no restriction | limiting in the water to wash | clean, Any of pure water, ion-exchange water, distilled water, and tap water may be sufficient, and the organic solvent melt | dissolved or mixed in water may be included.

The washing method in the washing step is not particularly limited, and it is preferable that the water-soluble substance is sufficiently removed. For example, it can be performed by immersing in water 5 to 10,000 times the weight of the molded product for 0.5 to 50 hours. At this time, washing efficiency is improved by stirring the water. Further, such a cleaning step may be repeated in order to further remove the water-soluble substance.

In this invention, after performing a washing | cleaning process, it is suitable to perform a dehydration and / or a drying process further as needed. The method and conditions for dehydration and drying are not particularly limited, and examples include dehydration by a filter, centrifugation, decantation, etc., heating by steam, electrical machinery, gas, infrared rays, etc., and a drying method by vacuum decompression, etc. It is preferable to carry out until the weight of the cured porous gypsum does not change.

The cured porous gypsum obtained by the production method of the present invention has a low density and is sufficiently porous, and has a high surface area. Therefore, it is useful for various uses such as building materials and water purification materials. In particular, since it is excellent in adsorption performance and carrying performance, it is extremely useful as an adsorbent or recovery material for various elements (for example, P, Pb, As, etc.) for soil, water quality, and sludge purification materials. Thus, the porous gypsum hardened body obtained by the production method of the present invention, the adsorbent containing the same, the recovery material, and the water purification material are also one preferred form of the present invention.

Here, since water such as drainage, sewage, and rivers may contain heavy metals such as lead (Pb) and arsenic (As) in addition to phosphorus (P), purification treatment is necessary. The cured porous gypsum of the invention is particularly useful as a water purification material in that it has excellent performance for adsorbing and recovering these elements. Further, the cured porous gypsum of the present invention is excellent in phosphorus (P) adsorption / recovery performance, and can also realize more advanced water purification treatment. In this regard, phosphorus (P) in water such as drainage is deposited as calcium phosphate on the surface of the cured porous gypsum of the present invention. Since calcium phosphate has the ability to adsorb bacteria, in recent years, aerobic microorganisms in activated sludge widely used in sewage treatment plants, human waste treatment plants, septic tanks, etc. as a means of purifying wastewater and sewage have been treated with porous gypsum hardened bodies. It can be immobilized on the surface, and therefore, the use of the cured porous gypsum of the present invention makes it possible to perform a more advanced water purification treatment. That is, the water purification material using the cured porous gypsum obtained by the production method of the present invention is useful for the purification treatment of water such as drainage, sewage, and rivers. It is one of the inventions.

Examples of the building material include floors, walls, ceilings, roofs, pillars, beams, stones, surrounding edges, and decorative parts such as baseboards.

The porous gypsum hardened body preferably has an open porosity of 50% or more. That is, such a porous gypsum cured body having a large porosity can be suitably obtained by the production method of the present invention. The open porosity is more preferably 55% or more, still more preferably 60% or more.

In the present specification, the porosity means the ratio of the volume of the true solid portion and the gap (that is, the pore), and the pore is independent of the open pore connected to the outside and the inside of the object. There are closed pores. As defined in JIS R1634 (1998), the open porosity (%) means the percentage of the volume of the open pore portion occupied when the external volume of the sample is 1, and the following formula 1 Can be calculated. In this specification, a value measured in accordance with JIS R1634 (1998) is referred to as “open porosity (%)”.

In order to describe the present invention in detail, examples will be given below, but the present invention is not limited to these examples.

Example 1
(1) Slurry preparation process Hemihydrate gypsum was prepared for gypsum. Hemihydrate gypsum, water and sodium chloride were weighed as raw materials and mixed in the container. Subsequently, it stirred at 25 degreeC for 2 minutes so that the said raw material might become uniform, and produced suspension (slurry). The mixing ratio was such that the weight ratio of hemihydrate gypsum, water, and sodium chloride was (semihydrate gypsum: water: sodium chloride = 1.00: 0.64: 0.36).
(2) Molding step Next, the obtained suspension was poured into a cylindrical mold and allowed to stand at 25 ° C. for 5 hours to cure the suspension.
(3) Drying process The molding obtained by the molding process was taken out from the mold, put in a drier at 60 ° C., and dried for 24 hours to prepare a hardened gypsum body.
(4) Washing step Next, the obtained gypsum hardened body was immersed in 600 ml of water, and the water was stirred at 100 rpm for 12 hours to elute the solid content of sodium chloride precipitated in the molding step and the drying step. In addition, about the container, the said washing | cleaning process was repeated 3 times in order to fully remove the solid content of sodium chloride using a 1 liter beaker. Subsequently, the obtained gypsum hardened body was put in a dryer at 60 ° C. and dried for 24 hours to obtain a gypsum hardened body having a porous structure (porous gypsum hardened body).

Examples 2-6
Porous gypsum hardened bodies were prepared in the same manner as in Example 1 except that suspensions having different ratios of sodium chloride during the slurry preparation step were prepared and used. The ratio of hemihydrate gypsum, water and sodium chloride in the suspension is shown in Table 1.

Comparative Example 1
In the slurry preparation step, a hardened gypsum body was prepared in the same manner as in Example 1 except that the suspension was prepared and used without using sodium chloride. The ratio of hemihydrate gypsum and water in the suspension is shown in Table 1.

About each of the gypsum hardened | cured material obtained by each Example and the comparative example, open porosity (%) was calculated | required based on JISR1634 (1998). The results are shown in Table 1.
Moreover, all the hardened gypsum bodies obtained in Examples 1 to 4 and Comparative Example 1 were cut out to have a columnar shape with the same weight (about 1 g) and diameter (about 1.5 cm), and the diagonal direction on the front, the front direction and Photos taken from above are shown in FIGS.

From the examples and comparative examples, the following was confirmed.
The porous gypsum hardened body obtained in Examples 1 to 6 and the gypsum hardened body obtained in Comparative Example 1 differ only in whether a water-soluble substance (sodium chloride) is used as a raw material.
1 to 3 under these differences, the porous gypsum hardened body obtained in Examples 1 to 4 is more in number of holes (holes) than the gypsum hardened body obtained in Comparative Example 1. Obviously many (see especially FIG. 3). Moreover, although each gypsum hardening body shown in FIGS. 1-3 is all the same weight and diameter, the direction of the porous gypsum hardening body obtained in Examples 1-4 is clearly height (length). (See especially FIG. 2). Furthermore, it can be seen from Table 1 that the cured porous gypsum obtained in Examples 1 to 4 has a significantly higher open porosity than the cured gypsum obtained in Comparative Example 1. Similarly, it can be read that the porous gypsum hardened bodies obtained in Examples 5 and 6 are markedly porous (see Table 1). From these points, it was confirmed that the porous gypsum hardened body obtained in Examples 1 to 6 is significantly more porous than the gypsum hardened body obtained in Comparative Example 1.
Therefore, it was confirmed that the porous gypsum hardened body having a low density and a high surface area can be easily and inexpensively produced by the production method of the present invention.
In addition, since the porous structure of the porous gypsum hardened body is formed by elution of a water-soluble substance (in the example, sodium chloride is used), it is considered that all of the porous structure is composed of open pores.

Here, in the Example mentioned above, only the example which uses sodium chloride as a water-soluble substance is indicated. However, as long as a water-soluble substance is used, not only sodium chloride, the mechanism that the water-soluble substance is eluted and formed into a porous structure by the washing process with water after molding is the same. It can be said that the advantageous effects of the present invention are surely exhibited at least when a non-foaming inorganic substance (particularly preferably a metal salt) is used as the water-soluble substance.

Claims (8)

A method for producing a cured porous gypsum using at least gypsum, a water-soluble substance and water,
The manufacturing method is as follows:
A slurry preparation step of preparing a slurry containing gypsum, a water-soluble substance and water;
A molding step of obtaining a molding from the slurry;
The manufacturing method of the hardened porous gypsum characterized by including the washing | cleaning process wash | cleaned with water at least. The method for producing a cured porous gypsum according to claim 1, wherein the water-soluble substance is a non-foaming inorganic substance. The method for producing a cured porous gypsum according to claim 2, wherein the water-soluble substance is a metal salt. The method for producing a cured porous gypsum according to claim 3, wherein the water-soluble substance is at least one selected from the group consisting of sodium chloride and potassium chloride. The said slurry contains the said water-soluble substance of the quantity more than the saturation solubility in the temperature at the time of the said slurry production, The manufacturing method of the porous gypsum hardened body in any one of Claims 1-4 characterized by the above-mentioned. The said slurry contains 40-2000 weight part of water with respect to 100 weight part of gypsum, The manufacturing method of the porous gypsum hardened body in any one of Claims 1-5 characterized by the above-mentioned. The method for producing a cured porous gypsum according to any one of claims 1 to 6, wherein the cured porous gypsum has an open porosity of 50% or more. A water purification material comprising a cured porous gypsum obtained by the production method according to claim 1.